基于球单元组合颗粒模型的筒仓卸粮速度场演化机理研究

Study on the evolution mechanism of silo unloading velocity field based on ball element composite particle model

由于现有的单一球单元模型不能客观反映颗粒之间以及颗粒与筒仓仓壁之间接触的实际情况,本文提出了一种组合颗粒模型。以室内卸粮物理试验为基础,基于该组合颗粒模型进行离散元模拟,研究了卸粮速度场的时空变化,并对比分析了仓壁动态压力变化。研究结果表明:(1)改进的组合颗粒模型相比传统的ball单元模型,卸粮时间大幅增加,且动态侧压力波动幅度增大;(2)组合颗粒模型相比原模型中心颗粒垂直速度更小,而仓壁处颗粒由于剪切带颗粒堆积,两模型的垂直速度并无明显差别;(3)颗粒的水平速度波动与仓壁的动态压力波动呈同种变化趋势,且组合模型颗粒水平速度变化幅度较原模型更大;(4)组合模型由于颗粒间空隙较小、摩擦较为充分,在中心卸粮过程中会周而复始地出现压力拱现象,因此其中心颗粒的转动角速度(较仓壁处)的增长幅度更大。本文建立的组合颗粒模型能更准确地模拟筒仓卸粮动态物理特征变化,可广泛应用于粮食散体细观力学模拟等领域。

Because the existing single spherical element model cannot objectively reflect the actual situation between particles and the contact between particles and the bin wall,a composite particle model is proposed based on the physical experiment of grain unloading in the laboratory.The discrete element simulation is carried out based on the composite particle model,the spatial and temporal changes of grain unloading velocity field are studied,and the dynamic pressure changes of the storehouse wall are compared and analyzed.The results show that,firstly,compared with the traditional ball model,the improved composite particle model can significantly increase the time of complete grain unloading and the fluctuation range of dynamic lateral pressure.Secondly,compared with the original model,the vertical velocity of the central particle of the composite particle model is smaller,while the vertical velocity of the two models is not significantly different due to the accumulation of particles in shear zone at the bin wall.Thirdly,the horizontal velocity fluctuation of particles and the dynamic pressure fluctuation of the bin wall show the same variation trend,and the variation range of the horizontal velocity of particles in the combined model is larger than that of the original model.Fourthly,in the combined model,due to the small gap between particles and sufficient friction,the pressure arch will occur repeatedly in the process of central grain unloading,so the rotational angular velocity of the central particles increases more than that of the bin wall.The composite particle model established in this paper can more accurately simulate the dynamic physical characteristics of grain unloading in silo,and can be widely used in the field of grain granular mechanics simulation.